1. Field of the Invention
This invention relates to a contact image sensor for carrying out a reading operation in a facsimile, scanner, etc., and more particularly to an improved sealed structure for a light emitting light source as well as for a contact image sensor.
2. Description of the Related Art
FIG. 9 of the accompanying drawings is a cross-sectional view of a prior art contact image sensor disclosed in Japanese Patent Laid-Open Publication No. HEI 5-110760. The prior art contact image sensor comprises a housing 1, a rod-like light source 2 fixed to a detachable part 3 of the housing 1, a condenser lens 4, an image sensor 5, a glass plate 6, and a circuit board 7.
The operation of the prior art contact image sensor will now be described.
The light emitted from the rod-like light source 2 passes the glass plate 6 and is irradiated onto a detection surface of a detection object or document 8. Depending on the brightness of color of the document 8, a white surface reflects the light. The reflected light passes through the glass plate 6, is concentrated by the condenser lens 4, and is received by a light-receiving portion of the image sensor 5. Characters, etc. of the document 8 can then be read by the circuit board 7.
The glass plate 6 partitions the interior of the housing 1 from the exterior to prevent any foreign matter from the document 8 or surroundings from entering, thus securing the precision of the sensor and also serving as a support table for the document 8.
However, in the prior art contact image sensor, since the rod-like light source situated inwardly of the glass plate, which prevents the invasion of any foreign matter as mentioned above, is spaced apart from the document by a relatively large distance, a high-brightness light source is required to prevent the lowering of illumination efficiency.
Further, in order to allow the light to be irradiated onto the document or reflected back from the document and also in order to prevent any foreign matter from coming into the contact image sensor, a part of the contact image sensor must be covered with a transparent cover such as a glass plate.